Don't know if this helps. It is important to remember that the radial blue
line is based on sea level, on a standard day, at max gross weight. Change
any of the parameters and the blue line is inaccurate.
Bob Gardner
§ 23.1323 Airspeed indicating system.
(a) Each airspeed indicating instrument must be calibrated to indicate true
airspeed (at sea level with a standard atmosphere) with a minimum
practicable instrument calibration error when the corresponding pitot and
static pressures are applied.
(b) Each airspeed system must be calibrated in flight to determine the
system error. The system error, including position error, but excluding the
airspeed indicator instrument calibration error, may not exceed three
percent of the calibrated airspeed or five knots, whichever is greater,
throughout the following speed ranges:
(1) 1.3 VS1 to VMO/MMO or VNE, whichever is appropriate with flaps
retracted.
(2) 1.3 VS1 to VFE with flaps extended.
(c) The design and installation of each airspeed indicating system must
provide positive drainage of moisture from the pitot static plumbing.
(d) If certification for instrument flight rules or flight in icing
conditions is requested, each airspeed system must have a heated pitot tube
or an equivalent means of preventing malfunction due to icing.
(e) In addition, for commuter category airplanes, the airspeed indicating
system must be calibrated to determine the system error during the
accelerate/takeoff ground run. The ground run calibration must be obtained
between 0.8 of the minimum value of V1, and 1.2 times the maximum value of
V1 considering the approved ranges of altitude and weight. The ground run
calibration must be determined assuming an engine failure at the minimum
value of V1.
(f) For commuter category airplanes, where duplicate airspeed indicators are
required, their respective pitot tubes must be far enough apart to avoid
damage to both tubes in a collision with a bird.
[Amdt. 23-20, 42 FR 36968, July 18, 1977, as amended by Amdt. 23-34, 52 FR
1834, Jan. 15, 1987; 52 FR 34745, Sept. 14, 1987; Amdt. 23-42, 56 FR 354,
Jan. 3, 1991; Amdt. 23-49, 61 FR 5168, Feb. 9, 1996]
Post by O. Sami SaydjariPost by Scott Skylane/snip/Isn't there a way to judge true accuracy of
Post by O. Sami Saydjarispeed indicators (just as there is for altimeters)? Should I be
satisfied with my mechanic's answer and move on?
-Sami
N5554G, Cessna 421C
Sami,
There certainly are maintenance actions you can take to ensure your
airspeed indications are as accurate as possible. Both airspeed
indicators can be sent to an instrument shop for check/overhaul.
Arg. Sounds like a hard way of finding out.
Post by Scott SkylaneAny competent mechanic can check your pitot and static systems for leaks
and /or abnormalities.
Just did a Pitot Static check.
Post by Scott SkylaneOnce these are all done, your system will be as accurate as originally
designed. Keep in mind that *some* aircraft are designed so that one
side is accurate at lower speeds, and the other accurate at higher
speeds, but I doubt this is the case with a twin Cessna. The above info
does not infer whether the expense incurred would be worth the outcome,
that is a decision only you can make.
P.S. When did you sell your Turbo Arrow
I have not sold my beautiful Arrow yet.
Post by Scott Skylaneand get that bottomless money pit?
I got half-share in the C421 in mid-November. So, the good news is that
it is only a half-bottomless money pit :)
Post by Scott SkylaneHappy Flying!
Scott Skylane